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          05_Ribbon 负载均衡
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        <h3 id="1-概述"><a href="#1-概述" class="headerlink" title="1. 概述"></a>1. 概述</h3><p><strong>Ribbon 是什么</strong></p>
<p>Spring Cloud Ribbon 是基于 Netflix Ribbon 实现的一套<strong>客户端负载均衡的工具</strong>。</p>
<p>简单的说，Ribbon 是 Netflix 发布的开源项目，主要功能是提供客户端的软件负载均衡算法，将 NetFlix 的中间层服务连接在一起。Ribbon 的客户端组件提供一系列完整的配置项如：连接超时、重试等等。简单地说，就是在配置文件中列出 LoadBalancer（简称 LB：负载均衡）后面所有的机器，Ribbon 会自动的帮助你基于某种规则（如简单轮询，随机连接等等）去连接这些机器。我们也很容易使用 Ribbon 实现自定义的负载均衡算法。</p>
<hr>
<p><strong>Ribbon 能做什么</strong></p>
<p>LB，即负载均衡（Load Balance），在微服务或分布式集群中经常用的一种应用。 </p>
<p>负载均衡简单地说就是将用户的请求平摊的分配到多个服务上，从而达到系统的 HA（高可用）。 常见的负载均衡软件有 Nginx，Lvs 等等。Dubbo、Spring Cloud 中均提供了负载均衡，Spring Cloud 的负载均衡算法可以自定义负载均衡简单分类： </p>
<ul>
<li><p>集中式 LB</p>
<ul>
<li>即在服务的消费方和提供方之间使用独立的 LB 设施</li>
<li>如之前学习的 Nginx，由该设施负责把访问请求通过某种策略转发至服务的提供方</li>
</ul>
</li>
<li><p>进程式 LB </p>
<ul>
<li>将 LB 逻辑集成到消费方，消费方从服务注册中心获知有哪些地址可用，然后自己再从这些地址中选出一个合适的服务器。 </li>
<li><strong>Ribbon 就属于进程内 LB</strong>，它只是一个类库，集成于消费方进程，消费方通过它来获取到服务提供方的地址。</li>
</ul>
</li>
</ul>
<blockquote>
<p>Github 地址 ： <a target="_blank" rel="noopener" href="https://github.com/NetFlix/ribbon">https://github.com/NetFlix/ribbon</a></p>
</blockquote>
<span id="more"></span>

<h3 id="2-初步配置"><a href="#2-初步配置" class="headerlink" title="2. 初步配置"></a>2. 初步配置</h3><p><strong>先说结论</strong></p>
<p>&#x3D;&#x3D;Ribbon 和Eureka 整合后 Consumer 可以直接调用服务而不用再关心地址和端口号&#x3D;&#x3D;</p>
<hr>
<p><strong>步骤</strong></p>
<ol>
<li><p>复制<code>spring-cloud-consumer-dept-80</code>改为<code>spring-cloud-consumer-dept-ribbon-80</code></p>
</li>
<li><p>修改主启动类名字</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@SpringBootApplication</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DeptConsumerRibbon_80</span> &#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        SpringApplication.run(DeptConsumerRibbon_80.class, args);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
</li>
<li><p>添加依赖</p>
<figure class="highlight xml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">&lt;!-- eureka-client --&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework.cloud<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-cloud-starter-netflix-eureka-client<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.2.4.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"><span class="comment">&lt;!-- Ribbon --&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework.cloud<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-cloud-starter-netflix-ribbon<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>2.2.4.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></table></figure>
</li>
<li><p>修改 application.yml，添加 Eureka 的服务注册地址</p>
<figure class="highlight yaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">eureka:</span></span><br><span class="line">  <span class="attr">client:</span></span><br><span class="line">    <span class="attr">service-url:</span></span><br><span class="line">      <span class="attr">defaultZone:</span> <span class="string">http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/</span></span><br><span class="line">    <span class="comment"># 不向eureka注册自己</span></span><br><span class="line">    <span class="attr">register-with-eureka:</span> <span class="literal">false</span></span><br></pre></td></tr></table></figure>
</li>
<li><p>在主启动类中添加注解<code>@EnableEurekaClient</code></p>
</li>
<li><p>在 ConfigBean 中添加注解<code>@LoadBalanced</code>，使其在获取 Rest 时加入 Ribbon 的配置</p>
</li>
<li><p>修改 Controller中的地址。原来是固定的，现在有了 Ribbon 就不能固定，所以改成微服务的名字</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">REST_URL_PREFIX</span> <span class="operator">=</span> <span class="string">&quot;http://SPRING-CLOUD-PROVIDER-DEPT-8001&quot;</span>;</span><br></pre></td></tr></table></figure>

<img src="/blog/blog/posts/blog/posts/d16c64a/image-20200826140202238.png" class>
</li>
<li><p>启动，测试</p>
</li>
</ol>
<h3 id="3-真正实现负载均衡"><a href="#3-真正实现负载均衡" class="headerlink" title="3. 真正实现负载均衡"></a>3. 真正实现负载均衡</h3><img src="/blog/blog/posts/blog/posts/d16c64a/image-20200826144922483.png" class>

<p>Ribbon 在工作时分成两步</p>
<ol>
<li>选择 EurekaServer，优先选择在同一个区域内负载均衡较少的 Server</li>
<li>根据用户指定的策略，从 Server 的服务注册列表中选择一个地址</li>
</ol>
<p>Ribbon 提供了多种策略，比如轮询（默认），随机和根据响应时间加权重等等</p>
<hr>
<ol>
<li><p>新建两个数据库，类似<code>springcloud01</code></p>
</li>
<li><p>新建两个服务提供者，类似<code>spring-cloud-provider-dept-8001</code></p>
</li>
<li><p>修改配置文件、端口号等等</p>
</li>
<li><p>保证三个服务对外暴露的实例名是一样的</p>
<figure class="highlight yaml"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="attr">spring:</span></span><br><span class="line">  <span class="attr">application:</span></span><br><span class="line">    <span class="attr">name:</span> <span class="string">spring-cloud-provider-dept</span></span><br></pre></td></tr></table></figure></li>
</ol>
<h3 id="4-Ribbon-核心组件-IRule"><a href="#4-Ribbon-核心组件-IRule" class="headerlink" title="4. Ribbon 核心组件 IRule"></a>4. Ribbon 核心组件 IRule</h3><p><code>IRule</code>会根据特定算法从服务列表中选取一个要访问的服务</p>
<table>
<thead>
<tr>
<th>策略</th>
<th>描述</th>
</tr>
</thead>
<tbody><tr>
<td><code>RoundRobinRule</code>（默认）</td>
<td>轮询</td>
</tr>
<tr>
<td><code>RandomRule</code></td>
<td>随机</td>
</tr>
<tr>
<td><code>AvailabilityFilterRule</code></td>
<td>会先过滤掉由于多次访问故障而处于断路器<strong>跳闸</strong>的服务，还有并发的连接 数量超过阈值的服务，然后对剩余的服务列表按照轮询策略进行访问</td>
</tr>
<tr>
<td><code>WeightedResponseTimeRule</code></td>
<td>根据平均响应时间计算所有服务的<strong>权重</strong>，响应时间越快服务权重越大，被选中的概率越高，刚启动时如果统计信息不足，则使用<code>RoundRobinRule</code>策略，等待统计信息足够，会切换到<code>WeightedResponseTimeRule</code></td>
</tr>
<tr>
<td><code>RetryRule</code></td>
<td>先按照<code>RoundRobinRule</code>的策略获取服务，如果获取服务失败，则在指定时间内会进行<strong>重试</strong>，获取可用的服务</td>
</tr>
<tr>
<td><code>BestAvailableRule</code></td>
<td>会先过滤掉由于多次访问故障而处于断路器跳闸状态的服务，然后选择一个<strong>并发量最小</strong>的服务</td>
</tr>
<tr>
<td><code>ZoneAvoidanceRule</code></td>
<td>默认规则，复合判断 Server 所在区域的性能和 Server 的可用性选择服务器</td>
</tr>
</tbody></table>
<hr>
<p>修改策略，在 ConfigBean 中添加（消费者服务）</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Bean</span></span><br><span class="line"><span class="keyword">public</span> IRule <span class="title function_">myRule</span><span class="params">()</span>&#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">RandomRule</span>();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<hr>
<p>自定义策略（消费者服务）</p>
<p><strong>需求</strong></p>
<p>依旧轮询策略，每个服务器要求被调用5次，就是以前每一个机器一次，现在每个机器5次</p>
<p><strong>实现</strong></p>
<ol>
<li><p>新建包 myrule，<strong>和 springcloud 包同级</strong>。新建类</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MySelfRule</span> &#123;</span><br><span class="line">    <span class="meta">@Bean</span></span><br><span class="line">    <span class="keyword">public</span> IRule <span class="title function_">myRule</span><span class="params">()</span>&#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">HorsenRule</span>();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
</li>
<li><p>新建一个类，设计 HorsenRule 这个策略</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br><span class="line">84</span><br><span class="line">85</span><br><span class="line">86</span><br><span class="line">87</span><br><span class="line">88</span><br><span class="line">89</span><br><span class="line">90</span><br><span class="line">91</span><br><span class="line">92</span><br><span class="line">93</span><br><span class="line">94</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> com.horsen.myrule;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> com.netflix.client.config.IClientConfig;</span><br><span class="line"><span class="keyword">import</span> com.netflix.loadbalancer.*;</span><br><span class="line"><span class="keyword">import</span> org.springframework.context.annotation.Configuration;</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> java.util.List;</span><br><span class="line"><span class="keyword">import</span> java.util.concurrent.ThreadLocalRandom;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> Horsen</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HorsenRule</span> <span class="keyword">extends</span> <span class="title class_">AbstractLoadBalancerRule</span> &#123;</span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * total        总共被调用的次数</span></span><br><span class="line"><span class="comment">     * currentIndex 当前提供服务的机器序号</span></span><br><span class="line"><span class="comment">     * &lt;p&gt;</span></span><br><span class="line"><span class="comment">     * total=0 当total数等于5以后, 指针才能往下走</span></span><br><span class="line"><span class="comment">     * index=0 当前对外提供服务的服务器地址</span></span><br><span class="line"><span class="comment">     * 如果total等于5, 则index+1, 将total重置为0</span></span><br><span class="line"><span class="comment">     * 我们只有3台机器, 所以total&gt;3时, 将total置为0；</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">private</span> <span class="type">int</span> <span class="variable">total</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">int</span> <span class="variable">currentIndex</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> lb 选择的随机算法</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">public</span> Server <span class="title function_">choose</span><span class="params">(ILoadBalancer lb, Object key)</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (lb == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">Server</span> <span class="variable">server</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">//查看线程是否中断了</span></span><br><span class="line">        <span class="keyword">while</span> (server == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (Thread.interrupted()) &#123;</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 活着的服务</span></span><br><span class="line">            List&lt;Server&gt; upList = lb.getReachableServers();</span><br><span class="line">            <span class="comment">// 获取所有的服务</span></span><br><span class="line">            List&lt;Server&gt; allList = lb.getAllServers();</span><br><span class="line"></span><br><span class="line">            <span class="type">int</span> <span class="variable">serverCount</span> <span class="operator">=</span> allList.size();</span><br><span class="line">            <span class="keyword">if</span> (serverCount == <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// int index = chooseRandomInt(serverCount); // 生成区间随机数</span></span><br><span class="line">            <span class="comment">// server = upList.get(index); // 从活着的服务中, 随机取出一个</span></span><br><span class="line">            <span class="keyword">if</span> (total &lt; <span class="number">5</span>) &#123;</span><br><span class="line">                server = upList.get(currentIndex);</span><br><span class="line">                total++;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                total = <span class="number">0</span>;</span><br><span class="line">                currentIndex++;</span><br><span class="line">                <span class="keyword">if</span> (currentIndex &gt;= upList.size()) &#123;</span><br><span class="line">                    currentIndex = <span class="number">0</span>;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 从活着的服务中, 获取指定的服务执行操作</span></span><br><span class="line">                server = upList.get(currentIndex);</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="keyword">if</span> (server == <span class="literal">null</span>) &#123;</span><br><span class="line">                Thread.yield();</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="keyword">if</span> (server.isAlive()) &#123;</span><br><span class="line">                <span class="keyword">return</span> (server);</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            server = <span class="literal">null</span>;</span><br><span class="line">            Thread.yield();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> server;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 随机</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">protected</span> <span class="type">int</span> <span class="title function_">chooseRandomInt</span><span class="params">(<span class="type">int</span> serverCount)</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> ThreadLocalRandom.current().nextInt(serverCount);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Server <span class="title function_">choose</span><span class="params">(Object key)</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> choose(getLoadBalancer(), key);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line"> <span class="meta">@Override</span></span><br><span class="line">		<span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">initWithNiwsConfig</span><span class="params">(IClientConfig clientConfig)</span> &#123;</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
</li>
<li><p>在主启动类添加注解<code>@RibbonClient(name=&quot;SPRINGCLOUD-PROVIDERDEPT&quot;,configuration=MySelfRule.class)</code></p>
</li>
<li><p>启动，测试</p>
</li>
</ol>

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